1. Field of the Invention
The present invention relates to an electrical box for providing electrical power to a building, and more particularly relates to an electrical box that enables efficient electrical wiring of a building using highly reliable electrical connection methods.
2. Discussion of the Background
In providing electrical power to commercial and residential buildings, a main power line typically carrying 100-200 Amps of 220VAC single phase power enters the building from an electric company power grid and is connected to a service box that distributes power to the entire building. In the service box, the 220VAC power is center tapped with a neutral return to provide two 110VAC sources of opposite polarity and ground terminal connected to the earth.
In the service box, power from the main power line is divided into branch circuits each of which typically provides 110VAC power circuit breakered at 15 to 25 Amps to several plugs, switches, and/or other electrical units located in different areas of the building. In providing such branch circuits, multi-conductor electrical cable must be routed from a branch circuit breaker in the main service box to electrical boxes that contain each of the electrical units in the branch circuit. The multi-conductor cable used to route the branch circuits typically includes a white insulation neutral wire, a black insulation hot wire, and a bare or green insulation ground wire to carry 110VAC throughout the building. In branch circuits, in which 220VAC are used, a red insulation alternative hot wire is also provided in the multi-conductor cable, and higher currents are allowed for certain high power appliances, such as stoves, ovens, air conditioners, heaters and clothes dryers.
Current practice in wiring a branch circuit is to route individual segments of the multi-conductor electrical cable from the interior of one electrical box to the interior of a subsequent electrical box in the circuit. When all electrical boxes are connected with cable segments, the free ends of the cable segments at the interior of each box are connected to complete the branch circuit. In completing the branch circuit, the outer insulation sheathing is first stripped off of each free end of cable to expose the internal electrical wires, and the insulation is then stripped off of the end of each wire to expose the copper conductor of the wire. The bare conductors of each wire are then connected by use of twist-on connectors or by connecting the conductor to a switch, plug, or other electrical unit in the box and the cables are folded within the interior of the box to make room for the electrical unit.
Similarly, when a new load, such as an electrical outlet is added to an existing electrical circuit, wires of the existing circuit must be spliced into and reconnected by use of the added load. Specifically, in adding a load, the electrician must first cut an opening in the finished wall to reveal the existing electrical cable which is then cut to provide two ends of the cable which are inserted into an electrical box used for housing the electrical outlet to be added. In situations whereby the electrical cable is not long enough that the ends of the cable can reach the interior of the new electrical box, it may be necessary for the electrician to install at least one junction box to extend the ends of the cable. The ends of the cable are then prepared and the internal wires are stripped as described above. The wire ends are reconnected through the electrical unit in the box to complete the circuit, and the wires are folded into the new box as discussed.
These conventional methods of wiring a building, however, present a number of problems to the electrician and homeowner. First, from the standpoint of the electrician, the effort it takes to cut and route cable segments between electrical boxes, and then to strip-and reconnect the internal wires of the cable using the above-described method is very time consuming and labor intensive. In addition, in installing a new electrical outlet, existing wires may have to be extended by use of a junction box requiring extra time. In addition, because multi-conductor electrical cables have three or four individually insulated conductors bound together by an outer sheathing, the cable is stiff and difficult to fold into the electrical box in such a way that plugs, switches, and other electrical units will have enough room to fit in the box. This creates greater inefficiency and makes it difficult for the electrician to sufficiently align all of the plugs and/or switches in a multi-ganged box so that a cover plate can be placed over the electrical unit and box.
In addition to the above-described efficiency problems, a significant amount of wire is wasted in routing all branch circuits from one main service box to each branch circuit region that the service box is to power. For example, providing power to the top floor of a large home may require two 15 Amp branch circuits in which case two multi-conductor electrical cables need to be routed from the main service box located in the basement, for example, to the area powered by each circuit. Distributed service panels that may resolve this problem have not been feasible in such situations due to their expense and large size that is not desirable for living space. Although to a lesser extent, electrical wire is also wasted when cable ends must be extended to reach the interior of a new electrical box when adding a load to an existing circuit.
From the home or building owner""s standpoint, with the hundreds of electrical connections inside even a small house, the complicated method of cutting and stripping cables and internal wires as described above is likely to result in at least one poor connection that will eventually fail. The possibility of a poor connection is also present for the addition of new outlets. The failure of such a poor connection can be as benign as denying electrical service to all downstream electrical boxes in the circuit or as disastrous as causing a house to burn down. Moreover, nicking, or cutting into, of a conductor of each wire may occur each time insulation is cut off the wire to expose bare copper for the connection. This reduces the wire surface area available for carrying electrical current and can cause localized overheating, with the potential to start a fire. Reduced surface area may also cause a significant voltage drop that slows down motors, dims lights, or affects the operation of voltage sensitive appliances.
Finally, because the multi-conductor electrical cable enters each electrical box and must be folded within the box, space inside each electrical box is limited thereby limiting the number and sophistication of features offered by the electrical units used with the electrical box.
Based on the foregoing, there is a clear need for an electrical box that provides safe and reliable power to a home and/or commercial building.
There is also a need for an electrical box that allows electrical wires to be connected to an exterior surface of the electrical box without occupying space within the electrical box.
There is further a need for an electrical box that allows electrical wires to be connected to the electrical box with minimal cutting and stripping of insulation from the electrical wires.
Finally, there is a need for an electrical box that accepts large electrical units having sophisticated functions and allows easy alignment of electrical units within the electrical box so that a decorative cover can be attached to the electrical box.
According to one aspect of the invention, an electrical box is provided which includes a hollow container having an open end, an interior surface defining an interior space, and an exterior surface. A neutral connector and a hot connector are mounted on exterior bus bars mounted on the exterior surface of the container and are configured to receive the neutral and hot wire respectively of a multi-conductor electrical cable. A neutral conductive member and a hot conductive member are mounted on interior bus bars mounted to the interior surface of the container and electrically connected to the neutral and hot connector respectively. According to this embodiment, the exterior connectors receive electrical power from a multi-conductor electrical cable and transfer the power to an electrical unit connected to the internal conductive members without the multi-conductor electrical cable entering the interior space of the electrical box. The exterior connectors are preferably insulation displacement connectors (IDCs) and are mounted to exterior bus bars that contain high current screw holes that accept high current wire connectors used where the electrical power is higher than the current capacity of the IDCs.
According to another embodiment of the present invention, the interior bus bars, exterior bus bars, connectors and conductive members comprise a single circuit and the electrical box includes a plurality of single circuits. In this embodiment, the electrical box also includes removable tabs that transfer electrical power from one circuit to another circuit in the plurality of circuits.
According to yet another aspect of the present invention, the conductive members are rigid fingers that protrude from the interior surface of the electrical box such that the electrical unit is plugged into the conductive fingers when the electrical unit is mated with the electrical box. The conductive fingers may be uniquely configured such that only appropriate contacts of the electrical unit can mate with corresponding conductive members.
In another embodiment of the present invention, the interior bus bars, the exterior bus bars, and the removable tabs of the electrical box are configured to carry high current electrical power.
According to still another embodiment of the present invention, removable jumper tabs are provided to route electrical power between two electrical boxes placed adjacent to one another in order to gang the electrical boxes together.
According to another aspect of the present invention, an electrical box is provided which includes a means for containing an electrical unit, the means for containing having an interior surface defining an interior space, and exterior surface, a means for electrically connecting a neutral wire and a hot wire to the exterior surface, and a means for electrically connecting a neutral contact and a hot contact of the electrical unit to the neutral wire and hot wire respectively without the neutral wire and hot wire entering the interior space of the means for containing. The electrical box may also include a means for fastening the electrical box to a finished wall, a means for mating the electrical unit with the electrical box, or a means for fastening an electrical cable to the electrical box. In addition, the electrical box may further include means for covering the means for electrically connecting a neutral wire and a hot wire to the exterior surface of the means for containing, or a means for transferring electrical power from the electrical box to an adjacent electrical box by forming a multi gang electrical box.
According to yet another aspect of the present invention, a method for connecting an electrical load to an electrical circuit in a building is provided. The method includes locating electrical cable of the electrical unit, electrically connecting an electric box to the cable without severing the cable, and electrically connecting the electrical load to the electrical box such that electrical power from the cable is provided to the electrical load. The step of electrically connecting may include stripping a length of outer sheathing from the cable to expose interior wires of the cable, and press fitting at least one of the interior wires of the cable to knife connectors mounted on the electrical box. Moreover, the method further includes clamping the cable to the electrical box such that mechanical stress is relieved from the at least one interior wire connected to the knife connectors, or covering an area where the interior wire is connected to the knife connector.